A known glass breakage detecting sensor for a window glass is disclosed in JP3531474B. The breakage detecting sensor is provided at a door of a vehicle in order to detect breakage of a window glass. The breakage detecting sensor includes a carrier plate for supporting the window glass, a coil spring for biasing the carrier plate towards the window glass in an upward direction, a stopper pin fixed on the window glass and engaged with an engaging portion of the door when the window glass is raised to fully close a window, and a limit switch for outputting a signal when the carrier plate is moved a pre-determined distance.
When the window glass is broken, the stopper pin of the window glass is disengaged from the engaging portion of the door. Therefore, the carrier plate is moved further upwards by the biasing force of the coil spring. When the carrier plate moves upwards for a pre-determined distance, the limit switch outputs a signal. Hence, the breakage of the window glass is detected when the signal is outputted from the limit switch.
However, in the known glass breakage detecting sensor for a window glass disclosed in JP3531474B, for example, the stopper pin of the window glass may not completely disengage from the engaging portion of the door depending on the way the window glass is broken, which may result in the carrier plate, which supports the window glass, not moving sufficiently. Hence, the signal is not outputted from the limit switch and the breakage of the window glass may not be detected.
A need thus exists to provide a glass breakage detecting sensor that is not susceptible to the drawback mentioned above.